Lineage conversion from acute lymphoblastic leukemia to acute myeloid leukemia on rearrangement of the IgH gene in a patient with Down syndrome.

A patient with Down syndrome (DS) at the time of diagnosis of acute lymphoblastic leukemia (ALL) had a relapse with acute myeloid leukemia (AML) after 4 years of complete remission. Although the diagnosis was AML, the leukemic blasts at relapse showed an immunoglobulin H rearrangement that turned out to be identical to that of the initial ALL blasts. It is thought that the leukemic precursor cells of this patient had the potential to differentiate into both lymphoid and myeloid lineages. This case is important for investigating target cells for leukemogenesis in DS.